German Pat. No. 2164058 is directed to basic substituted 4-benzyl-1-(2H)-phthalazinone derivatives of the following formula ##STR2## wherein R is a hydrogen or halogen atom, a trifluoromethyl group, or a lower alkyl or alkoxy group and Z is a 4-perhydroazepinyl, N-methyl-4-perhydroazepinyl, 3-quinuclidyl, 3-tropanyl, 3-nortropanyl, N-methyl-3-pyrrolidinyl or N-methyl-2-pyrrolidinyl-methyl group, as well as the physiologically compatible acid addition salt. These compounds have an antihistamine action.